I Built a Java Version Manager by Fixing Other Tools' Open Bugs

Every Java developer knows the ritual. A JAVA_HOME export in one profile file, a different one in another. sdk use java 21 in this terminal, but the other terminal is still on 8. The build passes in your shell and fails in the IDE because the IDE launched from the dock and never sourced your init line. A teammate's "works on my machine" that turns out to mean "works on my shell."

I got tired of it, so I built , but for Java. This article is partly about what it does, but mostly about how I built it, because the process is the part I'd recommend to anyone building in a crowded tool category: I mined my competitors' bug trackers and turned their backlogs into my test suite.